This invention relates to sewing machines and more particularyly to an accessible vibration dampening stitch length regulator adapted for high speed sewing machines.
The control of stitch length for a high speed industrial sewing machine creates problems not known to lower speed machines. Industrial machines often have stitch length regulator mechanisms incorporating a toggle link beneath the bed in the feed drive connection. Generally the feed stop determining forward stitch length and the regulator lever which it abuts in these machines have been located in the standard upstanding from the bed so as to be conveniently located for manipulation by the operator. It has been found, however, that this location for the stop is so remote from the regulating toggle in the bed that excessively dangerous vibrations were occasioned during high speed operation.
A solution to this problem is to locate the stop abutment in the frame beneath the bed in close proximity to the stitch regulating toggle. In this manner the dynamic loads generated in the toggle mechanism can be transmitted to the stop in a short, stiff and direct path and absorbed by the frame. In the previously known sewing machines utilizing this type of stitch regulator mechanism the operator did not have access to the regulator member without being required to tip the machine back from its rest position or by inserting a screw driver into the bed. One machine exemplifying this arrangement is illustrated in Washburn, U.S. Pat. No. 3,357,384.
Moreover, when it is desirable to reverse stitch at the end of a seam, for example, the operator depresses the reverse feed lever. The reverse feeding lever is generally mounted to swing the toggle away from the stop abutment and passed the zero feed point and into the reverse feed condition of the toggle. When this occurs in the prior art the vibrations are no longer absorbed by the frame and large unbalanced vibratory forces and noise occur.